The present invention generally pertains to injection molding systems and methods and is particularly directed to hold pressure control and plastic material transfer in a stacked multi-parting injection molding system having desynchronized injection periods.
Stacked multi-parting injection molding system having desynchronized injection periods are described in U.S. Pat. Nos. 4,400,341; 4,464,327 and 4,539,171 to Jens Ole Sorensen, the named inventor herein. U.S. Pat. No. 4,400,341 teaches that the desynchronous operation of a reciprocal stacked molding system can be twice as fast as the operation of a single mold provided that the cooling time (C) is greater than or equal to the sum of time (I) during which the plastic material is injected, the time (E) during which the molded product is ejected, and the time (HP) during which hold pressure is applied. EQU C.gtoreq.I+E+HP (Eq. 1)
In a stacked multi-parting injection molding system in which left, left center, center, right center and right molding blocks are disposed for movement with respect to each other along a common axis, it may not be possible to meet this condition when the hold pressure time is substantial.